It is well known that phospholipids are a major component of cell membranes. It is also known that phospholipids form bilayers in cell membranes in which the hydrophilic heads of the phospholipids face outwards towards the exterior walls of the membrane and the hydrophobic tails face inwards. Other components in cell membranes include transmembrane proteins and cholesterol. Detection of interactions between analytes and cell membrane components is an area of continuous development as such interactions are critical to understanding cell signaling and transduction processes. Detection of such interactions may thus be used in screening modulators of signal transduction processes and for use in screening pharmaceutical activity.
Although many conventional assay methods work very well to detect the presence of target species, such methods are generally expensive and often require instrumentation and highly trained individuals, which makes them difficult to use routinely in the field. Furthermore, most commonly available assay methods do not provide information regarding interactions that occur at cell membranes or biomimetic interfaces. Thus, a need exists for assay devices and methods which are easy to use and detect interactions of analytes at interfaces that mimic those that occur at the external surface of cell membranes.
Recently, assay devices that employ liquid crystals have been disclosed. For example, a liquid crystal assay device using mixed self-assembled monolayers (SAMs) containing octanethiol and biotin supported on an anisotropic gold film obliquely deposited on glass has recently been reported. Gupta, V. K.; Skaife, J. J.; Dubrovsky, T. B., Abbott N. L. Science, 279, (1998), pp. 2077-2079. In addition, PCT publication WO 99/63329 published on Dec. 9, 1999, discloses assay devices using SAMs attached to a substrate and liquid crystal layer that is anchored by the SAM.
Although various methods have been reported for detecting target species in a sample, there are few methods which may be used to investigate interactions at interfacial membranes that mimic cell membranes. Therefore, a need exits for liquid crystal devices and methods which allow interactions of analytes at liquid crystal/aqueous interfaces that mimic cell membranes to be detected and amplified.